Just out of curiosity, is she using the same tool to measure her heart rate? IE, is she wearing a heart rate monitor on her own body, or is she using the heart rate monitors on each piece of equipment? That might also contribute to the variability.
Heart rate is a useful indicator. That said, it can vary day to day, based on hydration, sleep, medications, stress, etc. So I like to use RPE as well. Does your client have good body sense in general? If your client is feeling like she is working “easy” on a piece of equipment, she’s probably right!
There is a big difference between the bike and the stair climber as you can see. You would be the best person to determine the levels that are safe for your client. It is good to use both heart rate and RPE as you are doing. It is easy get winded on the stair climber as you are carrying your body upright against gravity.
You would need to consider your reasons for putting your client on the stairclimber, as well as making sure balance is good for that client. Taking everything into consideration and looking at the big picture of what you wish to accomplish will help guide you.
I too agree that an exercise performed while standing (stair climber) will result in a higher HR because more muscles are being activated. Mark definitely had some very good points as did all the others. Karin also had a good point that the 220 minus the age is just an average across the board and does not take into account the clients physical health. Another thing you might want to use is the Karvonon formula which takes into account a persons maximum heart rate and their resting heart rate.
To find ones resting heart rate (RHR) they would need to take their pulse for 1 minute at least 3 days (preferably 5 days) in a row after waking but before rising out of bed without an alarm waking the person up. Write these numbers down then add them and divide by 3 or 5 depending on how many days they took their RHR. This will give you the persons average resting heart rate (RHR).
220 minus age = maximum heart rate (MHR)
MHR minus RHR = HRR (heart rate reserve)
HRR multiplied by training % + RHR = bpm
Ex: 50 year old with a resting heart rate of 65 bpm who wants to train at 70%
220 – 50 = 170 (MHR)
170 – 65 (RHR) = 105 bpm (heart rate reserve)
105 X .70 + 65 = 139 bpm
As someone else already pointed out, use your best judgment. You know your client better than I do. If it is unsafe for your client don’t have them train that hard. Using the RPE may be another option.
Hope all of this helps!
160 is a little high, but if this is the first of second time for her in the stairclimber then it’s normal (you will need to monitor for any distress signs). HR on the bike will always be lower than the stairclimber for obvious reasons. Each person reacts differently to various intensity levels and what seems difficult for one person it might not be for another. If she is in good health condition and she feels comfortable at 160 bpm despite her age I wouldn’t worry too much. RPE scale is a great way of finding out how she really feels. The same goes for any of the other machines.
Mark is right on. The other thing to keep in mind is that the formula of 220 minus age for maximum heart rate is an average and can differ from person to person.